Changing nitrogen and carbon biogeochemical cycles as a consequence of climate change and anthropogenic eutrophication alter marine food webs of coastal areas in an unpredictable way. These changes often manifest in the dramatic shift from nutritious algae species to lipid-poor, harmful cyanobacteria blooms that may endanger current food webs including fisheries.  So far we don’t have a mechanistic understanding how lower trophic levels like zooplankton that rely on a lipid based metabolism beyond the tropics and on a protein based metabolism in the tropics, cope with such lipid-poor conditions.  Zooplankton organisms play a key role in the biological productivity of the ocean as they refine algae into protein- and lipid-rich food and thus link primary to fishery production while fueling the microbial loop with their exometabolomic waste products.  Previous compound-specific stable isotope work of my colleagues and me proved that in contrast to the slow lipid metabolism, the understudied amino acid metabolism in zooplankton rapidly adjusts when food concentrations are low or cyanobacteria are abundant.  This makes it the optimal tool to investigate the consequences of lipid-poor cyanobacteria blooms on the energy metabolism in marine food webs.  In the ZET-Change project the carbon and nitrogen flows through the amino acid and lipid pools of zooplankton species and communities will be quantified during cyanobacteria blooms in the Baltic Sea.  The effect on the population and ecosystem level will be tackled by exploring the exometabolomic waste product release in combined field sampling and ship based experiments and subsequent analysis using cutting edge technologies like Fourier transform ion cyclotron resonance mass spectrometry.